Solar energy collectors which absorb radiant energy for subsequent heating purposes are well-known. Those most commonly employed consist of an array of panels in which a plurality of fluid bearing pipes or ducts absorb the radiant energy to warm the fluid. The warmed fluid is then circulated through a heat exchanger or storage unit for subsequent use. Many such panels are rotated by expensive mechanical means to follow the suns rays. Other are fixed to a roof or wall and are thus more limited in the number of hours they can function each day. It is customary to add these panels to an existing building structure as a later modification. Such installations are expensive and increase roof loads.
The efficiency of a solar panel system in a locality is determined by the percentage of energy available which is devoted to useful purposes. From an economic standpoint, the cost of the energy per Langely is determined by the cost of the abosorber plus upkeep. The thermal efficiency of the absorber can be computed in two ways, first, the ratio of the energy absorbed from the sun to the energy lost by conduction, convection and radiation, or by the ratio of the energy available to these losses. Since the angle of incidence of the solar energy will change during the day from sunrise to sunset, the percentage of energy which is devoted to useful purposes will be in direct relationship to the amount of such energy which can be converted by the structure of the panel.
In U.S. Pat. No. 3,951,128, there is shown a solar heat collector system incorporated into a roof or wall structure element having elongated elliptical or parabolic grooves therein. Flat elliptically shaped conduits are located above the parabolic grooves, which grooves are provided with reflective plates so that sunlight falling upon the collector system is directed upon the conduits and also upon the parabolic reflectors. The reflectors, in turn direct the reflected solar energy toward the conduits. In this prior art device, low angles of radiation incident upon the collector system will not be reflected onto the conduits and the percentage of energy which can be absorbed by the conduits is basically that which is received directly.
In still another prior art device, shown in U.S. Pat. No. 4,006,731, there is shown a roof structure in which parabolic reflectors are used to concentrate the sun's rays upon conduits located above them. However, these reflecting, surfaces are designed to compensate for sloping roofs and other architectural installations rather than to maximize the amount of solar energy received within the panel throughout the day.
It is therefore, an object of the present invention to provide solar energy collectors which are constructed as part of the exterior walls or roofs of buildings.
Another object of the present invention is to provide solar collectors which, while fixed in place, will absorb solar energy over a substantial portion of the day.
A further object of the present invention is to provide solar collectors in which the absorber-reflector structure is incorporated into conventional building materials, thereby reducing costs.
Still another object of the present invention is to provide structural building elements for exterior use which may subsequently serve as part of a solar energy collector.